JPH025756B2 - - Google Patents

Abstract

1. A process for the production of alpha-epoxides having from 11 to 24 carbon atoms by the reaction of aliphatic alpha-olefins having from 11 to 24 carbon atoms with performic acid which has formed in situ from formic acid and hydrogen peroxide, under elevated temperature, with stirring of the reaction mixture and with the metered addition of hydrogen peroxide, characterised in that the reaction is carried out at a temperature of from 40 to 90 C in the absence of solvents and catalysts, the aqueous phase and the organic phase are mixed by stirring until drops form, a concentration of more than 5% by weight of formic acid and a concentration of from 10 to 70% by weight of hydrogen peroxide is maintained in the aqueous phase for a period of a least 5 hours, the formic acid is used in a quantity of from 0.15 to 0.5 mol and the hydrogen peroxide is used in a quantity of at least 1.05 mol, in each case per mol of double bond to be epoxidized, and the hydrogen peroxide is metered in over a period of at least 3 hours.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention describes the process of preparing aliphatic α-olefins having from 11 to 24 C atoms with performic acid formed in situ from formic acid and hydrogen peroxide at elevated temperature under stirring of the reaction mixture. and a process for preparing α-epoxides having from 11 to 24 C atoms by reaction in the presence of hydrogen peroxide.

It has long been known to epoxidize esters of higher unsaturated fatty acids with internal double bonds, such as soybean oil, by reacting them in situ with performic acid formed from formic acid and hydrogen peroxide (U.S. Pat.
2485160 specification).

Application of the knowledge obtained in this process to the epoxidation of long-chain pure olefins (so-called α-olefins) having terminal double bonds failed because only poor yields were obtained. It has therefore been consistently pointed out in the literature that α-olefins cannot actually be epoxidized with performic acid produced in situ [Chemical Week, April 6]. Date (1963), No.
See page 60].

Finally, DE 15 68 016 A1 discloses a process in which α-olefins are epoxidized in situ in a water-immiscible solvent with aliphatic peracids formed in the aqueous phase. In this known process, the reaction mixture must be stirred particularly gently so that a unique interface is maintained between the two phases. Dispersion of the two phases under droplet formation must be absolutely avoided. A catalyst for forming the aliphatic peracid, such as sulfuric acid, is generally used together. Other aliphatic acids may also be mentioned, but acetic acid is used in all examples because it is particularly effective and particularly economical. Acetic acid is used in an amount of 0.5 to 1.5 moles per mole of double bonds to be epoxidized. This known process is expensive due to the use of solvents and the special care required during stirring and is extremely time consuming to achieve an acceptable yield.
Requires reaction time of up to 28 hours.

The object of the present invention is to provide an aliphatic α having 11 to 24 carbon atoms
- A process for preparing α-epoxides by reacting olefins with performic acid formed in situ from formic acid and hydrogen peroxide at elevated temperature with stirring of the reaction mixture and metered addition of hydrogen peroxide. and the method is characterized in that the reaction is carried out without solvents and catalysts, the aqueous and organic phases are mixed under stirring until droplets are formed, and more than 5% by weight is added in the aqueous phase for at least 5 hours. Formic acid concentration and 10-70% by weight
using less than 0.5 mole of formic acid and at least 1.05 mole of hydrogen peroxide per mole of double bond to be epoxidized, and hydrogen peroxide for at least 3 hours. It consists of adding an intermittent amount of.

The process according to the invention makes it possible to obtain the desired α-epoxides in very high yields within relatively short reaction times. The method is basically based on the number of C atoms.
It could also be used for less than 11 or more than 24 α-olefins. But C-number of atoms
With less than 11 α-olefins, the epoxide yield easily falls below 90% as a result of by-product formation. On the other hand, pure α- with more than 24 C atoms
Although olefins can be easily epoxidized by the process according to the invention, alpha-olefins often require additional use of solvents due to their high melting points.

The starting materials therefore used are olefins having from 11 to 24 C atoms which have double bonds in terminal positions and which react to form 1,2-epoxides.
Such olefins include, for example, 1-hendecene, 1-
Dodecene, 1-hexadecene, 1-octadecene or 1-eicosene. Mixtures of various α-olefins can equally well be used. The process according to the invention is particularly advantageous for preparing .alpha.-epoxides having 14 to 20 C atoms from the corresponding .alpha.-olefins.

The reaction is preferably carried out at a temperature of 40 to 90°C. In the case of large batches, measures must be taken to ensure that the heat of reaction liberated is sufficiently removed.

During the reaction, the aqueous and organic phases are broken until the phase interface is broken to form droplets. That is, the mixture is mixed by stirring so that droplets of the organic phase are distributed into the aqueous phase, and at the same time, droplets of the aqueous phase are distributed into the organic phase. Relatively lower olefins, especially C-atoms 11 or
For olefins with 12 carbon atoms, relatively gentle stirring is advantageous, whereas higher olefins with about 14 carbon atoms can mix vigorously with the aqueous phase and essentially form an emulsion.

In the process according to the invention, a formic acid concentration of more than 5% by weight must be maintained in the aqueous phase for at least 5 hours, preferably for the entire reaction time. This can be done by charging the entire amount of formic acid before the start of the reaction, or by charging a portion of the formic acid before the start of the reaction and adding the remaining amount during the reaction, or by adding the entire amount of formic acid during the reaction. This can be achieved by doing so.

The choice of any of the three possibilities mentioned above depends primarily on considerations of certainty. In any case, formic acid is partially charged and then during the reaction
It is advantageous to meter in such that its concentration in the aqueous phase is above 10% by weight, preferably from 10 to 20% by weight, at the start of the reaction. As the reaction progresses, the concentration of formic acid decreases and approaches the 5% by weight limit at the end of the reaction. Any concentration of formic acid can be used, as long as the condition of a minimum concentration of 5% by weight is maintained, depending, among other things, on the concentration of hydrogen peroxide used. It is advantageous to use formic acid in a concentration of at least 70% by weight. Preference is given to commercially available concentrations of 85 to 100% by weight. Formic acid is used in an amount of less than 0.5 mole per mole of total double bonds to be epoxidized. The minimum amount is usually 0.15 per mole of double bonds to be epoxidized.
Moles are sufficient. Preference is given to using 0.25 to 0.40 mol. A formic acid concentration of at least 5% by weight is maintained in the aqueous phase. A hydrogen peroxide concentration of 20 to 70% by weight, preferably 30 to 70% by weight, must be maintained in the aqueous phase within the same period of at least 5 hours. The concentration of hydrogen peroxide is also advantageously kept within the abovementioned range during the entire reaction time. The hydrogen peroxide concentration mentioned above is maintained by metering the total amount of hydrogen peroxide in sufficient concentration over a period of at least 3 hours. Hydrogen peroxide with a concentration of more than 68% by weight is used. Among these, hydrogen peroxide with a concentration of 80 to 90% by weight is particularly preferred if the process according to the invention is carried out in a single step. Hydrogen peroxide is used in an amount of at least 1.05 moles per mole of total double bonds to be epoxidized. An excess of hydrogen peroxide is preferably used and hydrogen peroxide is used in an amount of 1.2 to 2.5 mol, in particular 1.3 to 1.9 mol, per mole of double bonds to be epoxidized. After the end of the reaction, the dilute hydrogen peroxide present in the aqueous phase can be recovered by methods known per se, so that the actual consumption of hydrogen peroxide is approximately 1.05 to approximately 1.05 per mole of double bond to be epoxidized.
It's only 1.50 moles.

Formic acid concentration greater than 5% by weight in the aqueous phase and between 20 and 70
Olefin conversion is significantly lower if the weight percent hydrogen peroxide concentration is not maintained for at least 5 hours. Furthermore, the concentration of formic acid in the aqueous phase is below 5% by weight and/or the concentration of hydrogen peroxide is 20% by weight.
The olefin conversion rate is similarly low if it is less than . On the other hand, if the concentration of hydrogen peroxide in the aqueous phase is higher than 70% by weight, there is a risk of explosive decomposition.

When the above-mentioned conditions of the present invention are not met, for example, per mole of double bond to be epoxidized with formic acid.
If more than 0.5 mol is used, the olefin conversion rate does increase, but the yield (relative to the amount converted) and the yield (relative to the amount used) clearly decrease (see Comparative Example 4). If less than 1.05 moles of hydrogen peroxide are used per mole of double bonds to be epoxidized, the yield (relative to the amount converted) remains almost the same, but the olefin conversion and yield (relative to the amount used) clearly decreases (see Comparative Example 3). Furthermore, if hydrogen peroxide is not added slowly over at least 3 hours, but is added all at once, for example at the beginning, there is a risk of explosive-like decomposition, for example when using hydrogen peroxide at a concentration of 80-90% by weight. .
High olefin conversions and high yields (based on the amount used) can thus be obtained without danger within relatively short reaction times only if all the numerical conditions according to the invention are maintained.

The practical implementation of the method according to the invention presents different method technical measures. Maintaining the above concentrations of formic acid and hydrogen peroxide in the aqueous phase, for example,
This is facilitated by removing a diluted aqueous phase in proportions corresponding to the amounts of formic acid and hydrogen peroxide metered in from the reaction mixture via a phase separation vessel. This operation can be continued in the organic phase until the desired conversion is obtained. Such processes are one-step for the organic phase, but continuous for the aqueous phase. Another method is to carry out a conversion of the aqueous phase when the concentration of hydrogen peroxide decreases too much and the reaction rate becomes uneconomically small. Such a method is also a one-step process for the organic phase, but a two-step or multi-step process for the aqueous phase. Finally, there is one further embodiment. In this process, organic and aqueous phases are introduced into one another in a multi-stage countercurrent manner or in a mixer/settler set, i.e. fresh olefin is metered into a first device, where it is highly diluted. the aqueous phase, while in the last apparatus fresh formic acid and fresh, highly concentrated hydrogen peroxide are reacted with the already fully epoxidized organic phase. There are many variants of the technical method described above, ranging from batch implementation to fully continuous implementation.

The process according to the invention can be carried out without danger even on large industrial production plants, provided that certain safety measures are taken into account. Automatically opens and dilutes the batch with water, for example, if the mixing device malfunctions and the amount of exhaust gas formed by the decomposition of hydrogen peroxide or performic acid exceeds the limit value, or if the temperature significantly exceeds 90°C. A safety valve may be provided.

The reaction of the olefin with the performic acid formed in situ is preferably carried out without pressure. Generally reaction times of 5 to 20 hours, especially 8 to 10 hours are required.

After completion of the epoxidation reaction, the aqueous phase is usually separated from the organic epoxide phase. For further purification, it is recommended to remove from the organic phase any hydrogen peroxide and formic acid still dissolved in this phase.
For this purpose, it is advantageous to wash twice in succession with water, the volume ratio of organic phase to washing water being in each case approximately 10:1. Higher α-epoxides have less water solubility, so cleaning can be carried out at elevated temperatures. Therefore, there is no need to cool the organic phase after the epoxidation reaction is completed. The water still dissolved in the organic phase after the last washing can be easily removed in a manner known per se, for example by mild heating under reduced pressure.

Uniform, short chain α- of 11 or 12 C atoms
When preparing α-epoxides from olefins, it may be advantageous in some cases to proceed the epoxidation reaction to almost no complete conversion, since in that case the formation of by-products is already occurring. This is because it may have already begun. The epoxidation reaction can be stopped after a conversion of eg 60-90%. The relatively low-boiling α-epoxide can then be separated by distillation from the relatively high-boiling α-epoxide and used together in the next batch. In this way, α−
High conversions of olefins and at the same time high epoxide yields are obtained.

If olefin mixtures or uniform long-chain α-olefins with more than 12 carbon atoms are used, high conversions and high epoxide yields can be obtained without special measures. For example, the epoxidation of α-C ₁₄ -olefins is already obtained in a yield of 96% with an olefin conversion of about 96%. In the epoxidation of α-C ₁₈ -olefin, the olefin conversion rate is approximately 96
The yield below % is 99%.

The epoxides produced by the process according to the invention are so pure that they can be used directly for most applications. However, it is of course possible, if desired in particular cases, to carry out further purification in a manner known per se, for example by total distillation under reduced pressure.

The dilute aqueous phase remaining after separation of the organic phase can be worked up in a manner known per se to recover the hydrogen peroxide contained.

Next, the present invention will be explained in detail with reference to examples.

Example 1 α-C ₁₂ -olefin and α as starting materials
A commercially available olefin portion consisting of _-C14 -olefin (140 mol = 321) was used. Reactor (volume
50) consists of a stirred vessel with formic acid and hydrogen peroxide dosing vessels, exhaust gas measuring device and thermometer, with phase separation device in the lower discharge part, built-in heat exchanger, attached dosing pump. Temperature during all tests
It was maintained at 60°C.

First, over the course of 2 hours, 80% by weight hydrogen peroxide
84.0 mol (=2.67) and 17.5 mol (0.70) of 98% by weight formic acid were metered in. Further after dispensing
Stirred after 1.5 hours. At this point hydrogen peroxide was present in the aqueous phase at a concentration of 38% by weight.

A continuous process is then started for the aqueous phase, i.e. 80% by weight hydrogen peroxide and 98% by weight formic acid are metered in continuously and at the same time corresponding portions of the aqueous phase are introduced via a phase separation vessel. I took it out.
The composition of the extracted aqueous phase is 38-40% by weight of hydrogen peroxide, 1.5-3.5% by weight of performic acid, 8-12% by weight of formic acid,
It varied depending on the amount of water remaining.

After a total reaction time of 12 hours (2.0+1.5+8.5 hours), an epoxide content of 91.8% by weight and a residual olefin content of 3.9% by weight were determined in the organic phase. interrupt the reaction,
After phase separation, the organic phase was washed twice with three portions of water each time.

80% by weight total - 300 moles (9.5) hydrogen peroxide
and 98% by weight - 63 moles (2.42) of formic acid were used. The total amount of aqueous phase discharged was 10.6.

Example 2 4000 mol (1300) of α-C ₁₈ -olefin were used as starting material. The apparatus consists of an enameled 2 m ³ stirred vessel equipped with the additional equipment mentioned in Example 1. For safety reasons, an automatic quick-closing valve was connected to the elevated vessel filled with water. The heat of reaction was removed via an external condenser, through which part of the reaction mixture was constantly circulated. Epoxidation was carried out at 60°C in three steps with a total reaction time of 10 hours.

In the first step (3.5 hours), 88% by weight hydrogen peroxide
78.5 and 98% by weight formic acid 19.5 (precharged with 5) were used. Hydrogen peroxide and the remaining formic acid were metered in over the course of 2 hours. After the addition was complete, the batch was stirred for a further 1.5 hours. At this time the aqueous phase contained 34.5% by weight hydrogen peroxide, 8.5% by weight formic acid and 2.1% by weight performic acid. The aqueous phase was drained. The epoxide content in the organic phase was 42.5% by weight.

The second step was carried out in the same manner as the first step. After this time the epoxide content rose to 79.0% by weight. The discharged aqueous phase contains 36.1% by weight of hydrogen peroxide and 8.2% by weight of formic acid.
% by weight and 2.0% by weight of performic acid.

In the 3rd process (3.0 hours), in the course of 1 hour
33.5% by weight of 88% hydrogen peroxide and 15.5% by weight of formic acid were added.

After a post-reaction time of 2 hours, the aqueous phase discharged contains 36.1% by weight of hydrogen peroxide, 7.5% by weight of formic acid and 2.2% by weight of performic acid.
% by weight.

After carrying out the third step, dissolve the remaining organic phase in 100 ml of water each.
Wash twice in succession, then for half an hour.
Dry at 70mmHg. Epoxide content 95.8% by weight
and contained an olefin content of 3.2% by weight.

Example 3 2 moles (336 g) of α-C ₁₂ -olefin were dissolved at 70° C. in a 1-multi-necked flask equipped with a stirrer, two addition funnels, a thermometer, and a reflux condenser with a gas meter connected to the rear. and maintained at this temperature by a constant temperature bath. 98% by weight of formic acid 0.4 from the first dropping funnel during the course of 4 hours under stirring
mol (18.8 g) and 2.6 mol (104 g) of 85% by weight hydrogen peroxide were metered in from the second addition funnel. After the addition is complete, the batch is kept at 70°C for an additional 2 hours while stirring.
It was held at The two phases were then separated.

The aqueous phase contained approximately 30% by weight hydrogen peroxide, 1.5% by weight performic acid and 5.5% by weight formic acid. The organic phase contained 78.8% by weight of epoxide and 17.2% by weight of olefin.

The organic phase was washed twice with 30 ml of water each time and then partially distilled under reduced pressure, at a top temperature of 122°C.
(12 mmHg). A total of 64 g of distillate contained 96% by weight of olefin and 4% by weight of epoxide and were used together in subsequent batches. A total of 298 g of bottom product contained an epoxide content of 94.7% by weight. Subsequent purification fractionation (12 mmHg) yielded 99.5% by weight of epoxide as fraction 2.

Fraction 1: 120-124℃ = 16g Fraction 2: 124-125℃ = 264g Residue: > 125℃ = 18g Results: Olefin conversion 81.7% Yield (based on the amount used) 77% Yield (based on the amount converted) 94% Comparative Example The same procedure as Example 3 was carried out, but the following points were changed.

₁ If 40 wt% _H2O2 is used instead of 85 wt% _H2O2 , the amount of _H2O2 in _the aqueous phase will be 15.4 wt%, resulting in an olefin conversion rate of 17.1% Yield ( _amount used) ) 15% Yield (relative to the amount converted) 90%.

2 If 60% by weight formic acid is used instead of 98% by weight, the formic acid concentration in the aqueous phase will be 5.0% by weight,
The results were: Olefin conversion rate: 59.8% Yield (based on the amount used): 56% Yield (based on the amount converted): 95%.

3 Instead of the H ₂ O ₂ :olefin molar ratio of 1.3 according to Example 3, a molar ratio of 1.0 (in the claims >1.05
), the results are: Olefin Conversion 63.3% Yield (relative to the amount used) 60% Yield (relative to the amount converted) 94%.

4 HCOOC:Olefin molar ratio according to Example 3
Taking 0.154 as 0.7 (<0.5 in the claims), the results are: Olefin Conversion 88.9% Yield (relative to the amount used) 68% Yield (relative to the amount converted) 77%.

5 The acid temperature was 30°C instead of the reaction temperature of 70°C according to Example 3.
°C, the results are: Olefin Conversion 16.9% Yield (based on the amount used) 14% Yield (based on the amount converted) 82%.

The conversion rates and yields in Example 3 and Comparative Examples were obtained by analyzing the organic phase after washing by gas chromatography.

Example 4 α-C ₁₆ -Olefin 410 (1412 mol) was heated to 70° C. in a stainless steel stirred vessel capable of heating and cooling. The batch was then kept at this temperature while cooling. In reaction step 1, 1.4 formic acid (98% by weight) was added immediately and a further 12.2 was metered in uniformly over the course of 4 hours. Over the course of 3 hours, an amount of 51.4 ml of hydrogen peroxide (88% by weight) was added. After a total reaction time of 5 hours, the first reaction step was terminated and phase separation took place. The aqueous phase (51) was discharged. This is 33.6% by weight of hydrogen peroxide and 0.8% of performic acid.
% by weight and 5.7% by weight formic acid. The organic phase remaining in the stirred vessel is α-C ₁₆ -epoxide 70.4
% by weight and 28.8% by weight of α-C ₁₆ -olefin. Reaction step 2 was carried out immediately after phase separation. 0.5 of formic acid was charged and 4.3 was metered in over the course of 3 hours. Within a dosing time of 3 hours, 20% of hydrogen peroxide was also metered in with good mixing. After a total reaction time of 5 hours, the second reaction step was also interrupted. The discharged aqueous phase (18) contained 37.2% by weight of hydrogen peroxide, 0.4% by weight of performic acid and 4.3% by weight of formic acid.

The organic phase remaining in the container was washed twice with 30 ml of water (70 ml) each.
℃) and after removing the wash water, a small amount of dissolved water was removed by applying a vacuum (70 mmHg). Analysis of the organic phase thus dried can determine the epoxide content.
It gave 93.9% by weight and the remaining olefin 4.1% by weight.

Example 5 95 kg (404 mol) and 85% by weight of a mixture of α-olefin and vinylidene olefin having a carbon number of C ₁₆ to C ₁₈ (vinylidene content approximately 25%, iodine number 108)
- 3.95 Kg (73 mol) of formic acid were heated to 50° C. in a stirred vessel equipped with heating and cooling equipment. 80% by weight over the course of 90 minutes - 16.6 Kg (390.5 moles) of hydrogen peroxide
was added gradually, maintaining the temperature at 60°C. After the addition of hydrogen peroxide was completed, the mixture was further stirred at 60°C for 61/2 hours.

After cooling, the aqueous phase was separated and discarded. 85 in the organic phase
Weight % - 2.6 Kg (48 moles) of formic acid was added. After heating the mixture to 50 DEG C., 11.1 kg (261 mol) of 80% by weight hydrogen peroxide were added in the course of 90 minutes, the reaction temperature being adjusted again to 60 DEG C. The mixture was subsequently stirred at 60°C for 61/2 hours. The aqueous phase contained about 35.3% by weight hydrogen peroxide and about 6.7% by weight formic acid.

The organic phase was separated from the cooled reaction mixture and washed twice with hot water until the pH was 4, then 2 wt.
Treated with caustic soda solution 12. After fresh washing with hot water, the reaction product was vacuumed by a ring pump.
Dry by heating to 90°C at 30mmHg;
and finally filtered using a filter aid.

Epoxide oxygen content 5.83% by weight (of theoretical content
91.5%) and an iodine value of 3.72, 100 kg of a colorless epoxyalkane mixture were obtained.

Example 6 95 kg (404 mol) and 85% by weight of a mixture of α-olefin and vinylidene olefin having 16 to 18 C atoms (vinylidene content approximately 25%; iodine number 108)
- 3.27 Kg (60 mol) of formic acid were heated to 50° C. with stirring. Then within 1 hour 70% by weight - hydrogen peroxide 14.7
Kg (302.5 mol) were added, maintaining the temperature of the mixture at 60°C. This was followed by further stirring for 6 hours at 60°C.

After stopping the stirrer and phase separation, drain the aqueous phase;
Abandoned. 1.63 kg (30 mol) of 85% by weight formic acid was added to the organic phase. 70% by weight - 7.35 Kg (151 mol) of hydrogen peroxide during 1 hour at 60°C after heating the mixture
was added. The mixture was then stirred for 4 hours at 60°C. The aqueous phase was then separated and the process of the second step was repeated. The aqueous phase contained about 25.4% by weight hydrogen peroxide and about 5.9% by weight formic acid.

The reaction mixture was worked up as in Example 5, giving 100 kg of an epoxyalkane mixture with an epoxide oxygen content of 5.81% by weight (91.2% of the theoretical content) and an iodine number of 4.4.

Example 7 Tetradecene-1 (vinylidene content less than 1%)
78.7Kg (400 moles) and 85% by weight - 4Kg of formic acid
(74 mol) was heated to 50° C. with stirring. Continued 90
80% by weight in minutes - 15.3Kg of hydrogen peroxide
(360 mol) was added gradually, maintaining the temperature at 60°C. The mixture was then further stirred for 8 hours at 60°C.

The aqueous phase was drained. 85% by weight in the organic phase - 2 kg of formic acid
(37 mol) was added. After heating the mixture at 60℃
10.2 kg (240 mol) of 80% by weight hydrogen peroxide were added over the course of 90 minutes, and the mixture was then stirred at 60 DEG C. for 8 hours. The aqueous phase contains approximately 34.5% by weight of hydrogen peroxide and approximately 34.5% by weight of formic acid.
It contained 6.3% by weight.

The reaction mixture was worked up as in Example 5 to give an epoxide oxygen content of 7.1% by weight (94.4% of the theoretical content).
%) and an iodine value of 6.17. 83 Kg of clear tetradecene oxide were obtained.

Example 8 Tetradecene-1 78.7Kg (400 mol) Example 6
In three reaction steps, 85% by weight of formic acid (total of 6 kg (111 mol)) and 70% by weight of hydrogen peroxide29
Kg (597 mol) at 65°C. At that time, 50% of the total amount of formic acid and hydrogen peroxide was added in the first step.
And 25% each was used in the second and third steps.
The reaction time was 8 hours in the first step and 6 hours in each of the second and third steps. The aqueous phase is approximately hydrogen peroxide
21.7% by weight and about 5.3% by weight formic acid.

The reaction mixture was worked up to yield 82.5 Kg of tetradecene oxide with 7.24% by weight of epoxide oxygen (96.3% of theoretical content) and an iodide number of 3.85.

Claims (1)

[Scope of Claims] A peroxide formed in situ from an aliphatic α-olefin having 11 to 24 C atoms and formic acid in a concentration of at least 70% by weight and hydrogen peroxide in a concentration of at least 68% by weight. A process for preparing α-epoxides having 11 to 24 C atoms by reacting them with formic acid at temperatures of 40 to 90° C. with stirring of the reaction mixture and metered addition of hydrogen peroxide, in which the reaction is carried out. carried out without solvent and catalyst, mixing the aqueous and organic phases by stirring until droplets are formed;
Maintaining a formic acid concentration of greater than 5% by weight and a hydrogen peroxide concentration of 20-70% by weight in the aqueous phase for a period of at least 5 hours, with less than 0.5 mole of formic acid per mole of double bond to be epoxidized. and using hydrogen peroxide in an amount of at least 1.05 mol and characterized in that the hydrogen peroxide is metered in over a period of at least 3 hours. 2. A process according to claim 1, wherein a minimum concentration of 5% by weight of formic acid in the aqueous phase is maintained during the entire reaction time. 3. Adjusting the concentration of formic acid in the aqueous phase to more than 10% by weight at the beginning of the reaction, and reducing the concentration to 5% by weight at the end of the reaction over the course of the reaction.
The method according to claim 2. 4. The method according to any one of claims 1 to 3, wherein hydrogen peroxide is used in an amount of 1.2 to 2.5 mol per mol of double bond to be epoxidized.